COR 401 Lecture #11 Mechanisms of Inheritance February 17, 2009

1. COR 401 Lecture #11 Mechanisms of Inheritance February 17, 2009

2. German biologist/artist Ernst Haeckel (1834-1919),

5. Moore: If the hypothesis of evolution is true, only those variations that are inherited will be important

6. Even Aristotle knew about sex – But how is sex related to Wallace and Darwin?: Mechanism of Inheritance

7. Aristotle’s “Historia Animalium” ~350 BC

8. Aristotle’s Query: What is it exactly that parents transmit to their offspring?

9. Aristotle’s Male Semen/ Female Blood Coagulum Theory

10. A Cheesy Analogy Milk + Rennet = Cheese Male Semen (bearing “movement”) Sets the Female Semen (bearing “substance”)

11. Aristotle knew there was something up with the egg Oviparous Viviparous

12. Aristotle’s Embryology

13. Chick Embryology Time Lapse Video http://www.exploratorium.edu/traits/more.html

14. 48 vs 72 hr Chick Embryos “Blood is formed out of something that is not blood”

15. Aristotle’s Theory of Epigenesis Moore: Parents transmit not structures to their offspring but “information” (p 424)

16. Pangenesis: Every part of the adult body contributes some specific material to the semen which then configures the offspring If so: ? Why not produce 2 every time? ? How are they packaged to allow for multiple kids?

17. Aristotle: Modern Man in a Toga?

18. Fast Forward: 17th-18th C & Preformation Malphigi’s 2-Day Chick Embryo 1692 Hartsoeker’s Humunculus (1694) How could structures appear in the course of development from structureless material?

19. 12th C Virgin and Child Turkey

20. Epigenesis vs Preformation But if Preformist Theory is true: How can offspring be intermediate? And not this? Why this? If both sperm and egg preformed, why not 2 every time? ?

21. Epigenesis vs Preformation But if Preformist Theory is true: How to conceptualize Infinite regress? How to explain regeneration? If all from Eve, what about Human Variability

22. What about Dawkins’ Recipe and Blueprint Analogy ?

23. Which of the Following Statements Best Describes the Analogy: • A blueprint is like a scaled down version of an adult, • whereas a recipe if obeyed in the right order will • result in an adult. • 2. The blueprint corresponds one-to-one with the finished product • whereas there is no one-to-one correspondence between recipe • and final product. • 3. A blueprint implies set purpose and design, whereas a recipe • can deviate from the end product depending on the materials • and tools available in the kitchen. • 4. Of the two, the comparison between epigenesis and recipe is • more valid given the strong implication of the importance of • process – it’s all about information driving form/structure

24. Discovery of cells Robert Hooke’s Compound Microscope

25. Discovery of cells Van Leeuwenhoek’s Simple Microscope 1632-1723

26. Blending Inheritance: Offspring are an average of parents Dad Mom But then where do Darwin’s adaptations come from?

27. Gregor Mendel 1822-1884 Traits are controlled by heritable “factors” that we now call genes

28. Summary • Aristotle performed the groundwork in • suggesting that it is information, not • structure that is inherited • Aristotle’s epigenesis was challenged by • Pangenesis and Preformist Thinkers • Microscopes, put Preformist thought to rest • Darwin struggled with Blending Inheritance • as a mechanism by which adaptation would • prevail in the struggle for existence. • But it was Mendel who allowed us to • understand the gene and its mode of inheritance.